Itch (also known as pruritis) is a sensation that may be perceived as an unpleasant skin irritation and may drive an urge to scratch. Some itch is transient and is no more than moderately unpleasant. In some cases, however, itch can become chronic, significantly reducing quality of life. Conditions such as, for example, psoriasis, atopic dermatitis, renal failure, liver cirrhosis and some cancers may cause persistent itch. Accordingly, there is a need for improved compositions and methods for treating pruritis.